I've contacted Guo about the differences between the grenaditte and new voice trebles. I got a reply saying the different material affects the speed your air passes through it. Plus the crown and foot are silver in the gren. She asked if I've played either--honestly haven't even checked the local stores as I'm certain none have a treble sitting around.

But that got me wondering. Has anyone tried any of the Guo flutes (not just the treble)? I know Dr Potter tried their bass and found its playing to be acceptable although the keys are loud. And can anyone explain if there's any noticeable difference from air speed and crown material?

A couple years ago, I tried a Guo C flute at the NFA convention in Chicago. It was not grenaditte, so I assume it was a new voice. It played reasonably well and I suppose it would be fine for a beginning to intermediate flutist, but for me, I would not use it as my primary flute.

Regarding the marketing-speak about the material affecting the air speed, I would tend to say hogwash... Scientific studies by Benade and others have shown that in blind tests with identical flutes made of different materials, the material had no significant impact upon sound either to the player or the listener. Some players will attest that they can tell the difference between flutes made of gold, silver, or plated, but the scientific studies show that in blind tests where the players did not know which material they were playing, they were unable to reliably say which material was which. In fact, the studies showed that more often than not, the players incorrectly guessed the actual material. These studies also showed that bore dimensions and smoothness DID make a difference. So, perhaps these Guo flutes have different bore dimensions or smoothness and THAT could indeed account for a difference in sound more so than the material.

Crown material and various stopper designs may have some impact upon sound, but it is likely that the weight in the headjoint is responsible for the difference rather than the actual material. Different weights at nodal sound points may alter/enhance/diminish certain harmonics however, I have not seen any specific studies about that. It may be that a crown made of lead might produce a superior sound than plastic or even silver. I for one though will not be using a lead crown due to the health concerns associated with lead!

Here's Guo's response to my question about noticeable differences from the different air speed--

The grenaditte flute sounds more like a wooden one, with more deep tone. People who like to play jazz are saying that grenaditte flute gives the same tone as the jazz flutes 100 years ago.
And in case of new voice the sound is more similar to metal flute, its more light so to say,
The response is faster in Grenaditte flute. The keys react more faster

I'm a little curious what "jazz flutes 100 years ago" are--didn't they play concert flutes, same as orchestral flutists?

As for the diff, sounds like the cheaper new voice is what I'll aim for (unless a used metal treble comes up! ) Since I'll be playing it in a quartet with metal flutes, it should blend better than the woodier deeper grenaditte. Of course, by the time I've saved up the money, who knows what'll be available. Maybe Yami or one of the other flute companies will bring back a "real" (meaning metal) treble. Or maybe someone here will stumble across one. Ya just never know do ya?